If Armor Crush were "fused" into Aeolian Edge, then Aeolian, without question, would keep Huton refreshed 100% of the time while also being your highest damage combo finisher. That basically removes an entire job mechanic and travels into braindead territory. Why bother? Let's just go all out and just remove Huton and "fuse" it into NIN's permanent attack speed? This suggestion begins to oversimplify the job.
The only way I could see this suggestion being viable is if the effect were dependent on positioning. If Aeolian Edge hits from the rear, you get added damage, if it hits on the flank, you add Huton duration. However, even if that were to happen, you would have to look at other jobs that share the same types of positional bonuses and effects. Has NIN been simplified in comparison?
Personally I see no reason for a change to Armor Crush. As others have stated, it gets pretty consistent use, certainly more than once every 70 seconds. That's common knowledge. If you're waiting that long to use it, you're losing Huton and recasting it at some point. It doesn't completely refresh Huton, it just adds 30 seconds.